The most common and most likely answer to this crossword clue is the 7 letter word ARRIVAL
I've seen this crossword clue in The Times
A
R
R
I
V
A
L
More clues leading to the result ARRIVAL
- Appearance of a competitor, by the sound of it
- Emergence of a challenger to dictator
- Appearance of a Republican challenger
- Coming of a king and one who would like to overthrow him?
- Coming first in race, bumping into a fellow competitor
- A bishop merged with competitor for Advent
- Hear an adversary coming
- A Republican opponent’s appearance
- A c-competitor is coming
- Appearance of a competitor, say
Buddy explains!

The straight part
We know that "Appearance" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case appearance = arrival.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does ARRIVAL mean?
ARRIVAL noun- The act of arriving or something that has arrived.
- The attainment of an objective, especially as a result of effort.
- A person who has arrived.